In the World of Mutants
by TheMaskedTimelord
Summary: AU. After a large mutagen outbreak years ago, the world is full of mutants, humans becoming history. Our story centers around a family of mutant rats, and their friends, a family of mutant turtles. Despite how happy the two families are, their past finds a way to return and change their lives forever.
1. Prologue

**Author Note** : This story is based off of the picture "Family" drawn by 'yinller' from Deviantart. If you search on google "yinller tmnt family" it should be the first picture. I would actually use the picture for the story, but since I didn't draw the picture and I don't have a Deviantart account to ask yinller if I can use the picture, I'm going to play it safe. Unless you guys know for a 100% I can use it or something…

 **Disclaimer:** Turtles aren't mine, but I have created this AU based off of yinller's picture. If there is any other story with this type of universe, it is just a coincidence.

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 **Prologue**

Years ago, an alien race was working on a chemical that could somehow connect humans with their planet better. The aliens feared that the lifeforms would destroy their planet and decided this would help. Even though some have been working on the chemical, or mutagen as they call it, some of the aliens believed they should not interfere and let the lifeforms suffer the consequences. Unfortunately, fate made the choice for them. An accident occurred in space, causing the aliens to evacuate their spaceship; however, they had no time to retrieve their mutagen. Due to the many meteors in space, as well as no one taking care of the ship, it was destroyed and the mutagen fell to the Earth like rain. The mutagen has change all the humans on Earth, causing them to become part of the other lifeforms, the animals.

The humans, of course, did not understand how the green rain came or why it came. However, they continued to live their life, animals and humans becoming one. The aliens never interfered after that, believing the mutants on Earth were now on the right path. Some of the aliens also did not want to change the planet anymore than they already have.

Little did the aliens know how much evil could be in one being on that one planet. And that, is where our story takes place.


	2. Chapter 1

**Disclaimer:** Turtles aren't mine, but I have created this AU based off of yinller's picture. If there is any other story with this type of universe, it is just a coincidence.

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 **Chapter 1**

 **Hamato Yoshi's P.O.V:**

I let out a small sigh, breathing the fresh air and feeling the breeze on my fur. It is not often I come to this part of Japan; however, that does not mean I do not enjoy it. If it was not for the fact it was so far from my home, I would come here more. In the past, I have actually spoken to my wife, Tang Shen, about moving here. Sadly, we were unable to put that plan into motion. Besides, we are happy where we live now.

My rat ears twitch against my head as the sound of children begin to reach them. Even to this day, I continue to find advantages to being a mutant rodent, something my wife often agrees with. However, the random cravings for cheese that do plague my family are more of a chore than an actual privilege.

I can not stop the smile from crossing my face as I finally reach my destination. I walk toward the small home. It has a small yard as well as a small shed. One of my favorite parts about this home, though, is how easily they are able to explore in the woods. The friends that own the house always loved exploring and/or being part of the natural side of the world.

As I get close to the house, I spy the two small children I heard earlier playing in their front yard. They chase each other around in the grass, laughing and yelling at each other. I watch their joy and fun for a few minutes before the child in blue sees me. He gives me a small smile before running to the door, yelling inside. The other child in orange, who also has blue eyes like his brother and cheeks covered in freckles like his mother, sends me a wide smile that seems to cover his entire face. His eyes seem to glow as he gives me a huge wave. I chuckle lightly at his actions and tilt my head toward him in greeting.

"Ah! Yoshi-san!" I turn to the voice to find Matsui Akio leaving the house and moving towards me with his son in blue trailing behind. We have met years ago when we were taught Ninjutsu in the same Dojo. He has told me that his father sent him to the Dojo, teaching him how to protect the ones he love. Years after that, he went to America to learn more about being an engineer and mechanic before returning to Japan. We have always stayed and contact and became close friends. He was a tall turtle, his skin a dark shade of green. His eyes were almost red which was something that always intrigued people. Even though he has learned fighting all his life, he is not one to start fights. He says it is more for self-defense than anything.

"Akio-san. It's good to see you," I greet, giving him a bow which he gladly returns.

"And you as well," he says with a smile. He looks at his children. "Leonardo, Michelangelo, you two remember Splinter, right? He'll be staying for dinner."

Since I do not come here often, the children often have a hard time remembering me due to their young age. I look down at them and give them a friendly smile. Leonardo gives me a shy smile in return but stays close to his father. Michelangelo, however, gives a huge smile and nods quickly, bouncing slightly on his feet.

"Yeah! I remember you!" he cheers. "You did cool moves with Daddy!"

I chuckle lightly. When I usually stop by, me and Akio will end up sparring each other. One time, the children saw us fighting and tried copying our moves. This, of course, led to sore children and a couple broken vases. Akio and I received a long talk from Akio's wife, Narumi.

"Yes, Michelangelo," I agree. "But we may not be doing that today. After all, we do not want to make your mother angry again, now do we?"

The small turtle thinks for a moment before saying "Mommy yelled at you and Daddy a lot. It was funny!"

I laugh at the child's amused smile at the memory of an angry mother turtle yelling at an adult rat and her husband. I look at Akio to see him playfully shaking his head and Leonardo giving a small smile as well.

"Why don't we go inside?" Akio suggests, picking up Michelangelo and carrying him inside with Leonardo trailing close behind.

Even though they are a family of six, there house is not very big. The four boys shared a bedroom since they are still fairly young. There was a kitchen, a dining room, and also a small living room. Besides their bedroom, Akio and Narumi also have a room just for inventing equipment, similar to a laboratory of some sort. Of course, equipment they created that does not fit in the house either goes to the shed or in the backyard.

I have to avoid stepping on the toys that cover the floor as I follow my friend and his sons. I can't help but smile at the sound of the two other boys playing with each other somewhere in the house. Feeling a tug on my robe, I look down to find Michelangelo looking up at me with his big, blue eyes. Like his mother, his eyes hold joy and excitement. How he escaped his father's arms, I have no idea. His small, green arms hold a small toy elephant, pressing it close to his chest.

"Do you want to play?" Michelangelo asks innocently.

I chuckle lightly and rub his head. "Maybe later, little one. Why don't you try to play with your brothers until then?"

His smile grows a bit more at the idea. "Okay!" And with that, he runs to his brother, Leonardo, and pulls him down the hallway to their room, ignoring his brother's wide eyes and confused expression. Akio and I chuckle at the sight.

"Is that Yoshi I hear?" I hear someone say from the kitchen.

I turn to find Narumi coming from the kitchen, rubbing her hands off with a towel. After sitting the towel on the nearby counter, she walks over towards me and her husband. Like Michelangelo, she is covered in freckles and has a lighter color shade of green. Her eyes are sharp green and there is the small gap between her teeth that have been there for as long as I remember. She also has a headband with a blue flower on. Narumi comes up to me and gives me a tight hug. She has always been energetic and social, despise her sad past.

After knowing Narumi for quite some time, she told me how she has been raised by her grandparents. Her mother died after giving birth to her and her father died years later. He use to work at a factory or compound before breathing in a type of toxic gas due to a malfunction with the equipment. A week later, he passed away in a hospital. Ever since then, she was raised by her grandparents and started growing an interest in chemistry, biology, and other branches of science. She self-taught herself a lot and learned as much as she could. Of course, after marrying Akio, she received news of her grandparents being in the hospital. Do to some past health issues and being at an old age, they both passed away not too long after Narumi received the news.

I return the hug and chuckle. "Kon'nichiwa, Narumi," I greet. "Thank you for inviting me."

She gives me a warm smile as she pulls away. "No problem! We enjoy having you here. Where is Shen and Miwa?"

"I'm afraid Miwa has been under the weather. Shen has been quite busy taking care of her."

"I'm sure Miwa will be back up and around in no time," Narumi says, leading us to the kitchen. "But Shen will need to stop by soon to make up for missing supper. This trouble-maker has me slaving around making food for you guys." She points at her husband with a smile.

"I help out!" Akio says defensively.

I laugh as they start to argue playfully. My ear twitches as I hear a noise behind me. I turn around just in time to see four pairs of eyes watching me down the hallway. After realizing I was watching them, they quickly disappeared back into their room. There is no possible way for me to stop the chuckle at seeing the turtle children.

"Akio, why don't you go get the kids? Dinner will be ready soon," Narumi says, catching my attention.

Akio replies with a nod, and heads down the hallway. I watch him walk away and I soon hear laughter coming from the room, causing me to release another set of light chuckling. This house is always filled with laughter and joy. Whenever I come over (whether it is by myself or with my family) I always end up leaving with a wide smile on my face.

It wasn't long till we were sitting down at the table, eating the food my friends have prepared for us. Michelangelo made it very well aware that he wished to seat by me. Oh course, not seeing any harm in it, we allowed him to sit on my right with his mother beside him. His blue eyes often find mind and he will give me a big grin behind the food that rests on his face. He will also ask me strange questions, getting slightly scolded for talking with his mouth full. A smile slowly crosses my face when Narumi tries to clean off his face with a rag, ignoring the child's protests.

Leonardo is sitting besides his mother, trying to eat politely unlike his brother. He holds his silverware strange and sometimes gets a small amount of food on his mouth, but you can tell he is trying to be neat. His storm blue eyes glance over to me and around his family, as if making sure everything was okay and in order. I have noticed how he shares the same color of green as his father, but that is the only physical characteristic he shares with them.

Besides Leonardo is Donatello. Instead of focusing on his food, Donatello is more focused on playing with his silverware. His eyes dart to me once and awhile, but he is more focused on other things. I can't help but notice how his skin is a slightly darker tint that his mother's and Michelangelo's, but he has a small gap between his teeth just like Narumi. His eyes, however, are red and unique, just like Akio's. Akio taps in front of Donatello, grabbing his son's attention, before pointing at the food. Obviously this is a fairly normal routine for Donatello gives a small pout before he slowly starts eating his food.

Between me and Akio sits Raphael. His skin is a dark green, but lighter than his brother's, Leonardo, and his father's. Green eyes, just like his mother's, would pay no mind to me, only looking up at me to observe me before finding something more interesting. I can't help but notice how he leans closer to his father. He has a hard time keeping some of his food on his silverware, giving it a glare when it did not cooperate. My friend jokes how the food is not his enemy before giving his son a hand. Raphael thanks him with a small smile before returning to his food.

"So, how have you been, Yoshi? It feels like forever since I have spoke to you last," Narumi says, trying to start a conversation.

"It has only been a month, Narumi," I correct with the smile.

"Well that is just too long," she replies quickly, playfully smacking Michelangelo's hand when he tries to take food off her plate. In response, he gives a light giggle.

"Not much has happened," I explain, taking a quick sip of water before continuing. "Shen has talked about going to New York."

"New York?" Akio asks, looking up from his plate. "That is quite different from our small, rural town in Japan. Why does she want to go there?"

"She believes there will be more opportunities available. You also know how she feels about Miwa growing up around ninjas."

"I want to grow up as a ninja!" Michelangelo exclaims. He lifts his fork up into the sky. "I would be a hero and save people and stop all the bad guys!"

"I'll be a cooler ninja!" Raphael suddenly says.

The two boys continue to see who can outdo the other while their parents and I chuckle at them. Leonardo watches the conversation with a mild amount of interest as Donatello ignores them. It wasn't too long before I was helping Narumi put the dishes away as Akio went to get the boys cleaned; or, he is, at least, attempting to. All that I can hear is the sounds of splashing mixing with the sound of children laughing.

"I will never understand how you two are able to deal with four small boys," I say as I dry a plate before putting it away. "There are many days that even Miwa becomes a handful.

"It keeps things interesting," she says with a playful smile. "I'm sorry we can't simply put the dishes in a dishwasher. Unfortunately, Donatello is starting to go into his 'break everything to see how it works phase.' He will definitely grow up to be an inventor."

I laugh. "It is fine, my friend. I'm glad to help after you have made such a wonderful dinner."

"I'm glad you enjoy it." She turns serious. "How have you and Tang Shen been doing? The last time I talked to her, you two have gotten into an argument."

"Even the closest friends have arguments," I simply say.

Narumi puts down the plate she was cleaning to walk over and hold my hands. "I know this is bothering you, Yoshi. Please do not try to hide it."

I lower my gaze. She has always been able to read someone's emotions ease. In truth, Shen and I have been fighting lately. She wants to leave Japan behind and start a new life. I understand her reasoning, but I do not like the idea. Part of me fears that the life I have been raised in will become forgotten. The fact that I will be leaving everything and everyone I know also does not settle with me.

I feel her three-fingered hand lift up my chin so our eyes connect, her green eyes holding kindness and understanding. "She is just getting use to everything. After some time, you two will be arguing on who should give little Miwa a bath."

I chuckle at her statement and give a small nod. Even in my darkest moments, she is able to come up with a way to make me laugh. Before I know it, she has pulled me into a hug.

After we have finished with the dishes and cleaning up the dining room, Akio comes out of the bathroom with four small turtles, dressed in cozy clothes and ready for bed. Donatello walks over to his mother, pulling her robe and saying "Mommy" softly. Narumi gives him a smile before kneeling down, leaning in close to her him as he whispers quietly. She gives a nod, whispers back to him with a smile before standing straight once more, taking her son's hand.

"Why don't you two go outside," she says, gesturing to myself and Akio. "I'll read these little trouble-makers a story before bed. Once the story is over, I'll come and get you."

"That sounds good," Akio replies with a smile. He gives his closest sons, Raphael and Michelangelo, a quick pat on the head before leading me to the back door. "Don't cause too much trouble for your mother!" he calls over his shoulder to his sons. The only response he receives is laughter and giggles from the small turtles.

Once Akio and myself reach the backyard, my friend leads me to their shed. Since there are four small children in their home, they normally leave their weapons in the shed or barn. Akio decides to have me wait outside while he went into the cluttered building. It appears that the couple is too busy to get it organized, or they keep putting it off. I can't help but chuckle at the sight as Akio jumps and moves over miscellaneous objects to get two large wooden swords for practice.

When me and Akio have practiced together as small children, the dojo we went to had many practice weapons. Years ago, when our Sensei was donated better equipment, he was willing to give his students some of his old equipment. While I took a beautiful katana (which still rests in my home) Akio took a couple practice weapons. Why he wanted them was, and still is, beyond me. Perhaps to have moments like this or so he can raise his children in the same art he has grown up in.

Once Akio hands me a wooden sword, we walk into the woods together. The woods always seem to give me a calm and secure sensation. I believe my friend can agree for he takes in a large breath and releases it with a sigh and smile on his face. "I love coming out here," he says, his smile bright and warm. "It's like we are the only ones in the world. No worries, no problems, just peace."

I nod in agreement. Even though my home doesn't have a wooded area or forest behind it, being in the country has always been more peaceful to me than living in the city. Not only was it a perfect place to practice ninjutsu, but it also created a wonderful scenery. Almost as if in a different world entirely.

As we come upon the familiar clearing in the woods, Akio stops in front of me. Giving me a warm smile and a bow, he quickly lifts up his sword, moving into an offensive stance. After copying his movement, he comes to strike at full speed. Over the years, I have noticed my friends technique. Having so much energy, he strikes his opponent at great speed in hopes of causing the enemy to slip or become unable to keep up. This technique has won him many battles; but, after sparring with him for years, I am able to keep up and become aware of what to look for. Of course, this gave my friend time to study my own method of fighting as well.

Finding an opening, I attempt to send a punch to his stomach. Apparently, predicting that move, he quickly dodges to the side before sweeping my feet from beneath me. Feeling the air escape my lungs, I do not allow my body to become stunned and roll to the side before jumping to my feet, dodging the wooden sword he sent my way. Our eyes meet as he shifts back into another stance; he sends a challenging smirk, one I easily return.

We continue our battle for what feels like a joyful eternity, not even noticing the sky turning into a dark purple. A couple bruises and welts cover my arms and legs, but I pay them no mind and continue to spar against my friend, who is holding about the same bruises at me. It seems as if we were truly in an isolated world, our biggest problem being how to win this battle and boast it to the loser. Getting ready to send another strike to Akio with my wooden sword, I feel something connect with my shoulder. The force of what hit me causes me to stumble before looking down to see an arrow with a plunger on the end, sticking to my arm. The weapon would most likely only create another bruise, but it bring great shock to me.

Akio's laughter fills the woods and I send him an icy glare, ignoring the confusion that crossed my mind. His laughter was stopped short when a plunger arrow hits his leg, causing him to stumble from the force as well. Smiling at what Karma brought him, I turn to find the source of the arrows. On the hill is Naomi, holding another arrow in one hand and a bow in the other. A confident, proud smile lays on her lips as her eyes glisten in the moon's light.

"I hate to interrupt," she calls from her post, "but it's getting awfully late. Time for bed, Akio."

"We will follow you there, m'lady," Akio calls back, giving her a bow with one arm on his chest and the other behind his back, holding his wooden sword.

Seeing my moment of opportunity, I dash towards him before sweeping his legs from beneath him. With a loud "oomph," he falls to the ground, landing on his face. As he turns over to give me a glare, I can hear Naomi laugh and the corners of my lips turn upward.

"A good ninja is prepared for anything," I tell him, allowing the tip of the sword to touch the grass as I rest my hands on the top of the handle.

"A good ninja is not a jerk," he replies, still glaring at me. Allowing a chuckle to escape me, I reach down to help him up. A smile grows on his lips as he takes my hand. Together, we get him back on his feet and begin our journey back to his house. Even though I will most likely be walking home with only the moon's light to guide me, it has been well worth it. After we both had a family of our own and Akio and Narumi moved further away, it was hard to find time to truly spend time together. Luckily, due to our children growing closer together as friends, we have been able to see each other more. Still, I never take our time together for granted.

After Akio gives me a pat on the shoulder while Naomi gives me a hug (telling me to tell Tang Shen and Miwa "Hello" for her) I head home, looking forward to seeing my wife and daughter again. Reaching my home, I notice the light on and I pray Miwa is not up due to being sick. Walking through the door and shutting it behind me, I find Shen sitting on the couch, I bowl of popcorn resting in her lap as she listens to the radio next to her.

As I approach her, she greets me with a warm smile. Tilting her head upward, she allows me give her a gentle kiss on the lips as I pull away she whispers to me, "Miwa is in bed; her fever finally broke this afternoon."

"Good," I reply with a smile. I was earlier worried she would not have the opportunity to enjoy the outdoors. According to many, a storm is soon approaching.

"You and Akio sparred?" she asks me, looking at the marks that covered me. After receiving my nod, she asks me who won. Informing her it was me, of course, I help her up from the couch and walk with her to the bedroom, my arm wrapped around her shoulders. Indeed, today was quite wonderful.

 **Author's Note** : This was a story I worked on a while back. I may not be able to really work on it any time soon; I just wanted to see how people like you react to it. Let me know what you guys think!


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